1. Field of the Invention
The present invention is generally related to an image sensor and a manufacturing method thereof. More particularly, the present invention relates to an image sensor and a manufacturing method thereof for preventing light leakage between different pixels.
2. Description of Related Art
Conventionally, a charge coupled device (CCD) is generally used for a solid-state image sensor since the property of high dynamic range, low dark current, and well developed technology. A conventional CCD comprises a photodiode array, and pulsed voltage is applied to the charge stored by each photodiode, so as to output a corresponding electric signal. However, in recent years, complementary metal oxide semiconductor (CMOS) image sensor (CMOS Image Sensor, “CIS”) is substantially developed for being compatible with the manufacturing process of a CMOS transistor. Thus, CMOS image sensor having a chip including a photodiode and an MOS transistor is used as solid imaging devices. A CMOS image sensor can be easily manufactured and the chip size thereof can be reduced. In addition, the CMOS image sensor can be easily integrated on a chip having other peripheral circuits, and thus the cost and the power consumption of an image sensor can be reduced. In summary, a CMOS image sensor is preferable to a CCD in a low cost image sensing application, and therefore application of the CMOS transistor in the CMOS image sensor is greatly enhanced.
In a solid-state image sensor device, such as a CMOS image sensor described above, the problem of light leakage between different pixels is an important issue that may influence the photo sensitivity of the image sensor device. FIG. 1 is a cross-sectional view schematically illustrating a conventional image sensor device. Referring to FIG. 1, a conventional CMOS image sensor 100 includes a plurality of sensors 102, an inter-layer dielectric (ILD) layer 104, inter-metal dielectric (IMD) layers 106 and 108 having a plurality of metal 1 (M1) layers 112 and metal 2 (M2) layers 114 respectively, and a cover layer 110. The sensor 102 includes a photo sensor. For a CMOS image sensor 100, in general, the sensors 102, the M1 and M2 layers 112 and 114 are arranged as an array.
Hereinafter, the light leakage problem will be discussed. FIG. 2 schematically illustrates the crosstalk of the image sensor device shown in FIG. 1. Referring to FIG. 2, for example, the sensor 102a is used to receive the light 202 of the image. However, the lights 204 or 206 being incident from the neighboring pixels may also be received by the sensor 102a. Therefore, the crosstalk between the pixels in the image sensor is generated and thus the spatial resolution of the image sensor is low. Therefore, the photo sensitivity of the image is low. Accordingly, an image sensor that can prevent light leakage between different pixels to solve the problem of crosstalk is quite indispensable.